Isnt this the film Apocalypto? If so surely the bad guys coming behind the refugees will want to do some very evil things to the Terrans. Probably involving some kind of biological experimentation. Further developments will probably include a spurious escape from imprisonment, a long chase through the galaxy whilst picking off the baddies one by one Rambo style, before finally the remaining bad guys get distracted by the much larger worlds of the Imperium and leave the Terrans alone.
Not sure which film you're talking about. I looked "Apocalypto" up... it's a film about Mayans.
